The native or normal prion protein, designated “PrP” or “PrPc”, for the cellular prion protein is a glycoprotein broadly expressed in the lymphoid and neuronal cells of mammals.
Conformational changes of PrPc result in the appearance and propagation of the protein pathogen PrPc that is resistant to the proteinase K. This protein pathogen can be indifferently called “PrPsc” or “PrPres.” Accumulation of PrPsc in the organs of animals is at the origin of numerous diseases and especially of trembling in small ruminants, of the chronic cachetic disease (or chronic wasting disease “CWD”) of the elk and antelope, bovine spongiform encephalopathy (ESB) and Creutzfeld-Jakob disease (MCJ) in humans.
The delayed appearance after an incubation period of 2 to 6 years and slow development of symptoms in cattle infected with ESB has considerably slowed the development of epidemiological models. ESB is transmissible by ingestion to humans and has resulted in the appearance of a new form of Creutzfeld-Jakob disease (vMJC).
Detection of the protein pathogen PrPsc is difficult in infected animals healthy before the development of the disease and especially in the blood and urine of diseased animals. It has been established that PrPsc present in animals intended for human consumption is transmitted to man by ingesting infected tissues. Thus, a major objective of public health is to avoid this transmission by detecting the presence of PrPsc in animals intended for human consumption to remove them from the food chain.
Detecting the presence of PrPsc in biological samples or in animals has thus become extremely important and several research teams are developing methods of immunological detections (WO 02/086551). Moreover, methods of complexing peptides, small molecules or inhibitors to PrPsc to treat vMJC constitute the subject of active research. However, prior methods have constantly come up against the difficulty of identifying PrPsc in a reliable manner when it is in a low quantity in a biological sample.